string.c: fix for non-Unicode encodings

* string.c (rb_str_enumerate_grapheme_clusters): should enumerate
  chars for non-Unicode encodings.  [Feature #13780]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59731 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

string.c

@@ -8093,7 +8093,7 @@ rb_str_enumerate_grapheme_clusters(VALUE str, int wantarray)
     VALUE MAYBE_UNUSED(ary);
 
     if (!unicode_p) {
-	return rb_str_enumerate_codepoints(str, wantarray);
+	return rb_str_enumerate_chars(str, wantarray);
     }
 
     /* synchronize */

test/ruby/test_string.rb

@@ -903,6 +903,7 @@ CODE
 
     assert_equal ["\u000A", "\u0308"], "\u{a 308}".each_grapheme_cluster.to_a
     assert_equal ["\u000D", "\u0308"], "\u{d 308}".each_grapheme_cluster.to_a
+    assert_equal ["a", "b", "c"], "abc".b.each_grapheme_cluster.to_a
   end
 
   def test_grapheme_clusters
@@ -923,6 +924,7 @@ CODE
 
     assert_equal ["\u000A", "\u0308"], "\u{a 308}".grapheme_clusters
     assert_equal ["\u000D", "\u0308"], "\u{d 308}".grapheme_clusters
+    assert_equal ["a", "b", "c"], "abc".b.grapheme_clusters
   end
 
   def test_each_line